Abstract This project will create NHLBI COVID-19 common data elements and consensus outcomes to harmonize data practices across NHLBI and other COVID-19 studies. We will start with harmonizing data across two large NHLBI acute care clinical trial networks (PETAL, SIREN), and iterate, integrate, and promote these data harmonization standards with other COVID-19 research groups, including the international REMAP-CAP platform trial and other NIH institutes.